ARW size

[Geopram]

Hello to all,

Recently I purchased the a7iii and after some test-shootings I tried to convert the .arw image in .dng format through Adobe DNG Converter (so far so good). After the convertion I realized that despite the size of the original image (47mb), the new dng image was 24mb. Have anyone else noticed that or this was my mistake in Adobe DNG Converter?

P.S: I need this convertion cause i still use photoshop cs6 with adobe camera raw 6..6.

Thank you in advance

[tinplater]

I rarely shoot RAW but I do believe when I use DNG converter the same thing happens so I don't think you are doing anything wrong.

[Geopram]

Thank you for the answer. IT's trully strange. Parhaps an e-mail to Adobe will answer this....?

[Monochrome]

First, what are the settings you use for Preferences in Adobe Digital Negative Converter? These affect the size of the resulting DNG file. For example, if the JPEG Preview you include in the DNG is larger, the DNG is larger. If you set Preferences to "Use Lossy Compression", the DNG file will be smaller.

Second, are you using Sony's default ARW file format, which uses a lossy type of file compression? Or are you using Sony's UNcompressed ARW format? The uncompressed ARW files are about twice the size of the lossy ARW files. Which type of ARW file the camera uses is determined by settings in the camera's menu. Since you state the ARW files were about 47MB and the camera is an a7iii, I suspect you are using uncompressed ARW files.

Lossy means you can not get all the original information back when the file is uncompressed, as opposed to a non-lossy compression format which when uncompressed provides exactly all the original information. Lossy compression formats, such as JPEG, can give much smaller file sizes at the expense of discarding some of the original information.

If you are using Sony's lossy ARW file format but the DNG converter Preferences are non-lossy format, you may see little decrease in file size. If you are using Sony's uncompressed ARW file format, you will see substantial decreases in file size. How much smaller depends on how much information (think picture detail and noise) there is in the original uncompressed ARW. The more details or noise, the less the file can be compressed. A typical uncompressed ARW format file when converted to DNG with Preferences in Adobe DNG Converter set to NON-lossy compression results in a DNG file about half the size of the uncompressed format ARW file. Setting the DNG Converter Preferences to lossy compression will in this case give an even smaller DNG file.

DNG Converter can give smaller files because with the computing power of a "full" computer and a bit of extra time, it can do a better job of compressing the file. Your camera does not have nearly the same computing power nor do you want to wait a long time between taking each photo while the camera compresses the file.

If you want to have all the information the camera records, you need to have the camera menu set to use Sony's uncompressed format for the ARW files. These will average about twice the size of Sony's lossy ARW files. You can then later compress these with DNG converter. The resulting DNG files will be usually be smaller than a lossy ARW file of the same scene. How much smaller? If DNG converter is set to NON-lossy compression, they average slightly smaller that a lossy ARW file of the same scene. If the DNG Converter Preferences are set to lossy compression, they can be substantially smaller.

Sony's lossy format ARW files lose a bit of detail in the very deep shadows. I generally set my Sony camera to save in the uncompressed ARW format. Afterwards on the computer, I first decide what ARW files to delete. Then of the images I want to keep, I use DNG Converter set to non-lossy compression, medium JPEG, no embedding of original RAW (the uncomprssed ARW) and then compress the files. On the average, these are slightly smaller than Sony's lossy ARW files would have been and I still have all the original information that is lost in Sony's lossy compressed ARW files.

Note that if you use DxO Photo Lab and you want to use DxO's Prime noise reduction on high-ISO noisy files , you must keep the original uncompressed ARW file. The reason is DxO requires the original ARW file format to do the computationally-intensive Prime noise reduction. When I have this type of file, I do not bother with DNG conversion.

Edited December 21, 2018 by Monochrome